As a building material excellent in fire-safety, fire-resistance, sound insulation property, heat insulation property, constructability, strength, workability, decoration property and degradation-inhibiting property, a gypsum board has been widely used. In the gypsum board, a reinforcing material for the gypsum board is provided on one side or both sides of a core material mainly comprising gypsum, and the reinforcing material compensates for the weakness of the gypsum. A paper substrate has been generally used as the reinforcing material, and with the objective of further improving the above-mentioned properties, a non-woven fabric mainly comprising a glass fiber has been used (Patent literatures 1 and 2).
For a non-woven fabric used on both sides of a gypsum board as a reinforcing material, a certain extent of flexibility is required. If the flexibility of the non-woven fabric is poor, a crack may arise in the non-woven fabric during the manufacture of a gypsum board, and in some very extreme case, the non-woven fabric may be broken. The crack of the non-woven fabric leads to exudation of a gypsum slurry during the manufacture and to contamination around equipment such as a conveyer which transports the non-woven fabric, which causes problems of not only lowering the productivity but also reducing the strength of the gypsum board.
A non-woven fabric containing a glass fiber is excellent in strength and dimensional stability, and it has been conventionally used for the base material of a wallpaper or a floor material as a building material in addition to a gypsum board. However, when the content of the glass fiber is increased in order to improve strength and dimensional stability, the amount of the glass fiber to be exposed on the surface is increased, and the worker may feel irritation on his/her skin when handling it, which may become a problem.
On the other hand, for a building board material used for an interior material or an exterior material, including a gypsum board, it is an important requirement to have properties such as being lightweight, being a high strength, being smooth in surface and easy to be decorated with such as painting and wallpaper-pasting. A material the strength property of which is improved by reinforcement with a fiber, such as a fiber reinforcing-gypsum board which heretofore has been known, is a material in which a gypsum board is reinforced by a fibrous material. Thus, the strength property and workability are excellent; however, the material has a configuration in which a base material is exposed to the surface thereof, so that pretreatment such as sealer treatment is required to apply a surface decoration such as painting finish and wallpaper finish. Accordingly, a labor charge is generated on the painting work and this becomes a factor causing an increase in cost for the entire finish work. Moreover, a volatile component which affects the human body is contained in the sealer and the component diffuses during the painting work, so that the use thereof is tend to be limited. Also, for an interior material in which the decoration workability has a priority, a gypsum board coated with a paper board to which painting and wallpaper pasting are easily applied (a base paper for a gypsum board) has been widely used. However, the base paper for a gypsum board has a poor water resistance. When the base paper absorbs moisture, there are problems that peeling occurs between the layers of the base paper, etc.
[Patent literature 1] Japanese examined patent publication No. Hei 7-914
[Patent literature 2] Japanese unexamined patent publication No. 2002-285677